Heating device



H. c. GlLLEsPn-z March 30, 1943.

HEATING DEVICE Filed NOV. 29, 1941 nvntor. @alles/vlc G'ttorneg @nen/6.' y; I

Patented Mar. 30, 1943 HEATING DEVICE Henderson C. Gillespie, Moorestown, N. J., assignor to Radio Corporation of America, a corpora.-

tion of Delaware Application November 29, 1941, SeralNo. 420,956 7 Claims. (Cl. 219-13) This invention relates to heating devices, and more particularly to a device for heating conductive articles by induction from a source of electrical energy of high frequency, the present invention being in the nature of an improvement over that forming the subject matter of the copending application of Rudolph A. Bierwirth,y Serial No. 395,943, filed May 31, 1941, and assigned to Radio Corporation of America.

In the' aforesaid application, there is disclosed a heating device adapted for local rapid heating in many industrial applications. As described in il; can do no harm. on the other hand, the'prl- 'mary winding, which would be affected by water,

, is cooled vby dry air drawn from the surrounding that application, the device comprises a single'- turn coupling. coil which is coupled to a high frequency oscillator through a step-down transformer, the coupling coil providing" a high, concentrated magnetic field which induces eddy currents in a conductive article which is to be heated. Since the windings of the transformer become quite hot, a stream of compressed air is caused to pass over the windings to cool the same. The compressed air supplied by the compressor often contains moisture which,'when it settles on the windings, produces arcing between the turns thereof with consequent corrosion.

The primary object of my vpresent invention is to provide an improved heating device of this type which will not be subject to the foregoing disadvantage.

More particularly, it is an object of my present invention to provide an improved means for cooling the transformer windings and the coupling coil or inductor whereby efficient cooling will be obtained from an unfiltered air stream without damage tothe windings of the transformer.

A further object vof my present invention is to provide an improved heating unit and cooling system therefor as aforesaid which is simple in construction and highly emcient in use.

, In accordance with my invention, I employ an assembly comprising a multiple-turn primary winding, a single-turn secondary winding and a frusto-conical inductor tip connected to the latter, similar to the heating unit of the aboveidentified copending application. Instead of cooling the windings by a stream of compressed air, however, the required cooling air, according .to my invention, is blown directly against the inductortip through av nozzle arranged as an asplrator to draw, by suction, cooling air from the up for operation, the oscillator 5 supplies energy atmosphere.

The novel 4features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as toits organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of one embodiment thereof, when read in connection with the accmpanying drawing, in which i Figure 1 is a view, partly in section, of a heating device formed accordingto my present invention and coupled to a suitable source of energy,

Figure .2 is a sectional view taken on the line II-II of Figure 1, and

Figure 3 is a top plan view of the frusta-conical inductor tip, or coupling coil, according to my invention.

Referring more particularly to the drawing, wherein similar reference characters designate corresponding parts throughout, there is shown a spool-shaped supporting member l of insulating material on' which is wound the primary winding 3 of a transformer coupled to a suitable high frequency oscillator 5 by a concentric cable 1. Surrounding the primary winding 3 and spaced therefrom bythe annular flanges 9 and I l formed on the ends of the supporting member l-is a single-turn secondary winding I3, the windings 3 and I3 being concentrically related and the flanges 9 and H providing an annular air space `l5 between the two windings.

The primary winding 3 consists of a number of turns of wire of suitable diameter wound in a single layer on the supporting spool I, and the secondary winding I3 may be made of a lcopper sheet of suitable thickness and length, being formed into a tube which surrounds the primary winding 3, as clearly shown in Figure 2, and having one end thereof (the left-hand end, Figure 1) extending beyondthe adjacent end of the primary winding 3 and the flange 9. The' longitudinally extending terminals l3a of the secondary Winding i3 are, of course, in slightly spacedl relation, as clearly shown in Figure y2.

Secured to the-terminals I3a in any suitable manf inductor tip andy having a relatively-small diain- Y eter at its apex end nb. when the system is 'set the primary winding 3 whereby a high current is induced in the secondary winding I3 and the coupling coil I1 connected thereto. Since the coil I1 is of small diameter, particularly at its apex end I1b, there is set up at the apex end of the coil I1 a highly concentrated magnetic field. If, now, the coil I3 is brought into proximity with the article to. beheated, such as the head of a rivet I9 which is intended to unite a pair of sheets 2I and 23, for example, the rivet I3 will become heated because of the eddy currents induced therein by the aforementioned highly concentrated magnetic field. These eddy currents will be suillcient to explode a charge of explosive which has been placed'in the hollow shank of the rivet I9, thereby causing the rivet shank to expand slightly, as shown at Isa in Figure 1, and thereby firmly uniting the sheets 2i and 23.

To effect the proper cooling of the windings 3 and I3 and also the inductor tip I1, there is formed on the end of the secondary winding I3 which projects beyond the flange 9, and adjacent to the inductor tip I1, a radially inwardlydirected tubular member 25. This member may be formed either by spinning, or by brazing or otherwise suitably connecting it to the secondary winding I3. The secondary winding I3 is also provided with one or more circumferentially distributed openings I4, and the flange 3 is provided with a plurality of circumferentially distributed openings I0, the openings I4 affording communication between the atmosphere and the passageway I5, andthe openings I constituting additional passageways which afford communication between the passageway I5 and the tubular member 25. A nozzle 21 extends into the tubular member 25 and is of sufficiently small diameter to be spaced therefrom, the nozzle 21 facing radially outwardly of the secondary winding I3 and being connected by a hose 29 to a suitable source of compressed air, such as a storage tank 30 which is connected to a compressor 3|. A deilector plate 33 is also secured to the secondary winding I3 in spaced relation to the tubular member 25, the deflector 33 extending partly into the frusto-conical inductor tip I1.

When compressed air from the tank 30 is forced through the nozzle 21, that air, in passing through the tubular member 25, produces a vacuum in the passageways I0 and I5 which sucks in atmospheric air through the openings I4, as shown by the arrows in Figure 1. The atmospheric air combines with the compressed air in the tubular member 25 and both are deflected by the deilecting plate 33 on to the hot inductor tip or coupling Coil I1. Since the atmospheric air which passes along the primary winding 3 `in the passageway I5 contains practically no moisture, it will be obvious that the winding 3 will not be deleteriously affected thereby. At the same time, although the compressed air supplied by the tank 30 contains some moisture, this will be driven off by the heat of the inductor tip I1, and there will be no harmful result.

From the foregoing description, it will be apparent to those skilled in the art that I have' provided an improved heating device vwhich is capable of applying heat locally and with great efllciency to an article to be heated, while itself being adequately cooled without damage thereto..

Although I have shown and described but one embodiment of my invention, it will be apparent to those skilled in the art that many changes in ondary winding surrounding said primary winding in spaced relation thereto whereby to provide a passageway therebetween for passage of air. said secondary winding extending beyond said primary winding and including an inwardlydirected tubular member on its extension, means laffording communication between said tubular member and said passageway, a coupling coil of relatively small diameter connected to said secondary winding, and a nozzle adapted to be connected to a source of compressed air extending into said tubular member and facing outwardly therein, the compressed air passing through said nozzle and said tubular member serving to produce a vacuum in said passageway whereby to draw atmospheric air therethrough to eii'ect cooling of said windings. 2. In an electric heating device, the combination of a transformer including a primary winding adapted to be connected to a source of electrical energy and an elongated, single-turn, secondary winding surrounding said primary winding in spaced relation thereto whereby to provide a passageway therebetween for passage of' air, said secondary winding extending beyond the particular modification described, as well as said primary winding and including an inwardly radially extending tubular member on its extension, meansl providing a communicating passageway between said first-named passageway and said tubular member, a coupling coil of relatively small diameter connected to said secondary winding, and a nozzle adapted to be connected to a source of compressed air extending into said tubular member in spaced relation thereto and facing radially outwardly of said secondary winding, the compressed air emitted through said tubular member by said nozzle serving to ,create a vacuum in said passageways whereby to draw atmospheric air therethrough to effect cooling of said windings.

3. I'he invention set forth in claim 2 characterized in that said coupling coil comprises a frusto-conical member secured to said secondary winding adjacent said tubular member and extending beyond said secondary winding extension with the smaller end thereof located beyond the extremity of said extension, said frustoconical member being adapted to receive the compressed air and the atmospheric air passed through said tubular member.

4. The invention set forth in claim 2 characterized in that said coupling coil comprises a frusto-conical member secured to said secondary winding adjacent said tubular member and extending beyond said secondary winding extension with the smaller end thereof located beyond the extremity of said extension, said frusto-conical member being adapted to receive the compressed air and the atmospheric air passed through said tubular member, and charpassed therethrough v acterized in that said coupling coil comprises a frusto-conical member secured t said secondary winding adjacent said tubular member and extending beyond said secondary winding extension with the smaller end thereof located beyond the extremity of said extension, said y frusto-conical member being adapted to` receive the compressed air and the atmospheric air passed through said tubular member, and characterized further by the addition of a' deilector on said secondary winding constructed and arranged relative to said tubular member to direct the air passed therethrough onto said irusto-conical coil whereby to effect cooling of said coil.

6. In an electric heating device, the combination of an insulated tubular support, a winding thereon constituting the primary winding oi' a transformer adapted to be connected to a source of electrical energy, a single-turn, elongated conductive member surrounding said primary winding and constituting the secondary winding of said transformer, said secondary winding extending beyond said primary winding at one end, means maintaining said windings in concentric and spaced relation to each other whereby to provide a passageway therebetween, said secondary winding being provided with at least one opening adjacent its other end whereby atmospheric air may enter into said passageway, a radially inwardly extending tubular member on said secondary winding adjacent its ilrstnamed end, means providing a communicating passageway between said tubular member and said rst-named passageway, a nozzle adapted to be connected to 'a source of compressed air extending into said tubular member in spaced relation thereto and facing radially outwardly of said secondary winding, the compressed air emitted through said tubular member by said nozzle serving to create a vacuum in said passageways whereby to draw atmospheric air therethrough `to eiect cooling of said windings, a frustoprimary winding adapted to be connected to a source of electrical energy and a secondary windv ing inductively coupled to and spaced from said primary winding whereby to provide a passageway therebetween for the passage of air, one of said windings extending beyond the other of said windings, a a radially extending tubular member on theextension of said rst named winding, means aifording communication between said tubular memberl and said passageway, and a nozzle adapted to be connected to a source of compressed air extending into said tubular member and facing in a direction'such that the compressed air passing therethrough and thence through said tubular member will produce a vacuum in said passageway whereby to draw atmospheric air therethrough to eiIect cooling of said windings.

HENDERSON C. GILLESPIE. 

